Elevated 1-hour post-load glucose predicts cardiac autonomic dysfunction in non-diabetic individuals

Aims: Cardiac autonomic neuropathy (CAN) is a serious complication of diabetes, associated with increased cardiovascular risk. Recent studies suggest that postprandial hyperglycemia, particularly a 1-hour plasma glucose (1hPG) level ≥155 mg/dL during an oral glucose tolerance test (OGTT), could indicate early autonomic dysfunction even in non-diabetic individuals. This study aimed to assess whether non-diabetic subjects with elevated 1hPG levels exhibit impaired cardiac autonomic function compared to those with lower glucose levels.

Methods: This cross-sectional study included 88 non-diabetic participants from the Catanzaro Metabolic Risk Factors Study (CATAMERIS). Participants were divided into three groups based on their glucose tolerance: those with normal glucose tolerance (NGT) and 1hPG <155 mg/dL (NGT 1 h-low), those with NGT and 1hPG ≥155 mg/dL (NGT 1 h-high), and those with impaired glucose tolerance (IGT). Cardiac autonomic function was assessed using 24-hour heart rate variability (HRV) monitoring and cardiovascular autonomic reflex tests (CARTs).

Results: Participants in the NGT 1 h-high and IGT groups exhibited significantly worse metabolic profiles, including higher BMI, HbA1c, cholesterol, and triglycerides compared to the NGT 1 h-low group. HRV parameters (SDNN, SDANN, RMSSD, pNN50, Triangular index) were significantly reduced in the NGT 1 h-high and IGT groups, indicating impaired cardiac autonomic function. The prevalence of CAN, as diagnosed by CARTs, was also significantly higher in the NGT 1 h-high and IGT groups. Multivariate regression analyses revealed that 1hPG was the strongest independent predictor of reduced HRV and the presence of CAN, even after adjusting for other metabolic factors.

Conclusions: Elevated 1hPG levels (≥155 mg/dL) in non-diabetic individuals are associated with impaired cardiac autonomic function, similar to that observed in individuals with IGT. These findings suggest that 1hPG could serve as an important marker for early detection of cardiac autonomic dysfunction in non-diabetic individuals, potentially guiding earlier intervention strategies to reduce cardiovascular risk.

Comments. The study investigated whether non-diabetic individuals with a 1hPG level of ≥155 mg/dL during an OGTT show signs of CAN and reduced HRV, similar to those observed in individuals with impaired glucose tolerance (IGT). The results demonstrated that individuals with NGT but a 1hPG of ≥155 mg/dL had significantly worse cardiac autonomic function and a higher prevalence of CAN compared to those with lower 1hPG levels. The 1hPG level was found to be the strongest independent predictor of reduced HRV and the presence of CAN. The study highlights the significance of 1hPG ≥155 mg/dL as a marker for early detection of cardiac autonomic dysfunction in non-diabetic individuals, suggesting that this threshold should be considered in diagnostic criteria for prediabetes. Despite these clinically relevant findings, the study has some limitations, including a small sample size, the exclusive inclusion of Caucasians, the lack of age-related normal reference values for CARTs - which likely contributes to the high percentage of CAN diagnosis (up to 85% in NGT 1h-high) -, and the cross-sectional design, all of which limit the generalizability of the results. Further research is needed to confirm these findings and to explore potential preventive interventions.

Zoltan Kender

Reference. Monea G, Jiritano R, Salerno L, Rubino M, Massimino M, Perticone M, Mannino GC, Sciacqua A, Succurro E, Fiorentino TV, Andreozzi F. Compromised cardiac autonomic function in non-diabetic subjects with 1 h post-load hyperglycemia: a cross-sectional study. Cardiovasc Diabetol. 2024 Aug 10;23(1):295. doi: 10.1186/s12933-024-02394-w. PMID: 39127733; PMCID: PMC11316982.

https://cardiab.biomedcentral.com/articles/10.1186/s12933-024-02394-w